Ursodeoxycholic acid (UDCA) is a naturally occurring component of bile used clinically to treat primary biliary cirrhosis. In addition to treating various other liver diseases, UDCA and its taurine-conjugated derivative tauroursodeoxycholic acid (TUDCA) are anti-apoptotic agents that are known to have protective effects in animal models of multiple disorders including Huntington's disease, spinal cord injury, cataracts, and acute pancreatitis. The molecular mechanisms underlying the cytoprotective activities of these molecules are believed to engage a number of different pathways including preventing Bax-induced membrane perturbation in mitochondria, blocking caspase-3 activation, inhibiting calpain and caspase-12 activation caused by ER stress, and by modulating miRNA gene regulation.